Lithium ion secondary battery

ABSTRACT

A lithium ion secondary battery including a positive electrode including a lithium composite oxide represented by the general formula (1): Li x M 1-y L y O 2  (0.85≦x≦1.25 and 0≦y≦0.50; M is at least one selected from the group consisting of Ni and Co; and L is at least one selected from the group of alkaline earth elements, transition elements other than Ni and Co, rare earth elements, and elements of Group IIIb and Group IVb). The lithium composite oxide is treated with a coupling agent having a plurality of hydrolyzable groups, and the remaining hydrolyzable group is inactivated.

FIELD OF THE INVENTION

The present invention relates to a lithium ion secondary battery havingexcellent life characteristics.

BACKGROUND OF THE INVENTION

Lithium ion secondary batteries typical of non-aqueous electrolytesecondary batteries have high electromotive force and high energydensity. Thus, lithium ion secondary batteries are in an increasingdemand as a main power supply of mobile communication devices andportable electronic devices.

For the development of lithium ion secondary battery, it is an importanttechnical issue to enhance the reliability of the battery. A positiveelectrode of lithium ion secondary battery contains a lithium compositeoxide such as Li_(x)CoO₂ or Li_(x)NiO₂ (x is changeable depending oncharge and discharge of battery). These lithium composite oxides containCo⁴⁺ or Ni⁴⁺ having high valence and reactivity at the time of charging.Due to this, decomposition reaction of electrolyte pertaining to lithiumcomposite oxide is accelerated in a high temperature environment,generating a gas in a battery. Consequently, sufficient cyclecharacteristic or storage characteristic at high temperature cannot beobtained.

In order to inhibit the reaction between an active material and anelectrolyte, it is suggested to treat the surface of a positiveelectrode active material with a coupling agent (Japanese PatentLaid-Open Nos. 11-354104, 2002-367610, and 8-111243). This allows astable coating to be formed on the surface of active material particle.Therefore, the decomposition reaction of electrolyte pertaining tolithium composite oxide is inhibited.

Further, from the viewpoint of inhibiting the reaction between theactive material and the electrolyte and improving cycle characteristicand storage characteristic at high temperature, addition of variouselements to a positive electrode active material is suggested (JapanesePatent Laid-Open Nos. 11-16566, 2001-196063, 7-176302, 11-40154, and2004-111076).

Furthermore, improvement of water resistance is a problem regardingLi_(x)NiO₂. Therefore, it is suggested that a coupling agent is used tomake the surface of Li_(x)NiO₂ hydrophobic so that the stability of theactive material is enhanced (Japanese Patent Laid-Open No. 2000-281354).

The technology for inhibiting gas generation by using a coupling agenthas the following points to be improved. Many of lithium ion secondarybatteries are used for various portable devices. Various portabledevices are not always used immediately after battery charge iscompleted. There are many cases wherein a battery is kept in chargecondition for a long period, and thereafter discharge starts. However,the cycle life characteristic of battery is generally evaluated under acondition different from such practical use condition.

For example, a standard cycle life test is conducted in a conditionwherein a short rest (intermission) period is given after charging. Therest period is about 30 minutes, for example. If such condition isapplied for evaluation, the cycle life characteristic can be improved tosome extent by conventionally suggested technologies.

However, it is necessary to consider that intermittent cycles arerepeated on the assumption of practical use conditions. Ifcharge-discharge cycles are repeated with a longer rest period (e.g.rest period of 720 minutes) after charging, the above technologiescannot provide sufficient life characteristic. In other words, aconventional lithium ion secondary battery still has a problem, that isimprovement of intermittent cycle characteristic.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a lithium ion secondary battery thatcomprises a chargeable and dischargeable positive electrode, achargeable and dischargeable negative electrode, and a non-aqueouselectrolyte. The positive electrode includes an active materialparticle, and the active material particle includes a lithium compositeoxide represented by the general formula (1): Li_(x)M_(1-y)L_(y)O₂,wherein 0.85≦x≦1.25 and 0≦y≦0.50; M is at least one selected from thegroup consisting of Ni and Co; and L is at least one selected from thegroup of alkaline earth elements, transition elements, rare earthelements, and elements of Group IIIb and Group IVb. The lithiumcomposite oxide is treated with a coupling agent having a plurality ofhydrolyzable groups and the remaining hydrolyzable group that does notform a bond with the lithium composite oxide is inactivated.

When the lithium composite oxide is treated with the coupling agent, apart of the hydrolyzable groups usually remains uncombined to thesurface of the lithium composite oxide. The present invention has onefeature of inactivating the remaining hydrolyzable group by variousmethods.

In the general formula (1), when 0<y, L preferably includes at least oneselected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W andY.

The coupling agent is preferably a silane coupling agent. In this case,the coupling agent binds to the lithium composite oxide via Si—O bond.Thus, on the surface of the active material particle, a silicidecompound is formed.

The silane coupling agent preferably has as a hydrolyzable group atleast one selected from the group consisting of alkoxy group andchlorine atom, and further preferably has at least one selected from thegroup consisting of mercapto group, alkyl group, and fluorine atom.

The amount of the coupling agent is preferably 2% by weight or less withrespect to the lithium composite oxide.

The remaining hydrolyzable group is inactivated by a predeterminedstabilizer.

The remaining hydrolyzable group is inactivated by a reaction with, forexample, at least one hydroxyl group-containing substance (stabilizer)selected from the group consisting of inorganic hydroxide and inorganicoxyhydroxide. Here, as the hydroxyl group-containing substance, usableis at least one selected from the group consisting of LiOH, NaOH,manganese benzoate, and Mn(OH)₂.

The remaining hydrolyzable group is inactivated by reaction with, forexample, a ligating (coordination) compound (stabilizer) having two ormore reactive groups. In this case, each of the two or more reactivegroups preferably is hydroxyl group, carbonyl group, carboxyl group, oralkoxy group.

The remaining hydrolyzable group is inactivated by a reaction with, forexample, a silylating agent (stabilizer) having only one reactive group.In this case, the remaining group of the silylating agent is preferablyan organic group with a carbon number of 5 or less.

In treating the lithium composite oxide with a coupling agent, a part ofhydrolyzable groups of the coupling agent remains. Inactivation of theremaining hydrolyzable groups (for example, chlorine atom and alkoxygroup), improves intermittent cycle properties. It is supposed that theinactivation of the remaining hydrolyzable groups inhibits removal ofthe coupling agent or a compound derived therefrom the active materialparticle.

While the novel features of the invention are set forth particularly inthe appended claims, the invention, both as to organization and content,will be better understood and appreciated, along with other objects andfeatures thereof, from the following detailed description taken inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a vertical cross-sectional view of a cylindrical lithiumion secondary battery according to Examples of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

First, a positive electrode of the present invention is described. Thepositive electrode contains the following active material particles.

The active material particle contains a lithium composite oxide (Ni/Colithium composite oxide) including nickel and/or cobalt as a maincomponent. The form of the lithium composite oxide is not particularlylimited. The lithium composite oxide forms an active material particlein a primary particle condition, and in some cases forms an activematerial particle in a secondary particle condition. Secondary particlesmay be formed by agglomeration of a plurality of active materialparticles.

The average particle diameter of the active material particle (or Ni/Colithium composite oxide particle) is not particularly limited, but it ispreferably 1 to 30 μm, particularly preferably 10 to 30 μm. The averageparticle diameter can be measured by, for example, a wet laser particlesize analyzer available from Microtrac Inc. In this case, 50% value byvolume (median diameter: D50) can be considered as the average particlediameter.

The Ni/Co lithium composite oxide is represented by the general formula(1) Li_(x)M_(1-y)L_(y)O₂. The general formula (1) satisfies 0.85≦x≦1.25and 0≦y≦0.50.

Element M is at least one selected from the group of Ni and Co.

Element L is at least one selected from the group of alkaline earthelements, transition elements other than Ni and Co, rare earth elements,and elements of Group IIIb and Group IVb. Element L imparts an effect ofthermal stability improvement to the lithium composite oxide. Inaddition, element L is considered to have an effect of enhancing bindingpower between the coupling agent and the lithium composite oxide. Thus,element L is preferably present more abundantly on the surface layerthan inside the active material particle of the lithium composite oxide.

When 0<y, the lithium composite oxide preferably contains as elemen L atleast one selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb,Mo, W and Y. These elements may be contained in the lithium compositeoxide as element L either alone or in combination of two or morethereof. Among these, Al is suitable as element L since it has strongbinding power with oxygen. Mn, Ti, and Nb are also suitable. If elementL includes Ca, Sr, Si, Sn, B, and the like, it is preferable to includeAl, Mn, Ti, Nb, and the like at the same time.

The range x representing Li content may fluctuate in accordance withcharge and discharge of a battery. In the completely dischargedcondition, an initial condition immediately after battery assembly, or acondition immediately after the synthesis of lithium composite oxide,the range x may be 0.85≦x≦1.25, preferably 0.93≦x≦1.1.

The range y representing element L content may be 0≦y≦0.50. However,when the balance of the capacity, cycle characteristic, and thermalstability is taken into consideration, the range y is preferably0<y≦0.50, particularly preferably 0.001≦y≦0.35.

When element L contains Al, the atom ratio a of Al with respect to thetotal of Ni, Co, and element L is suitably 0.005≦a≦0.1, particularlysuitably 0.01≦a≦0.08.

When element L contains Mn, the atom ratio b of Mn with respect to thetotal of Ni, Co, and element L is suitably 0.005≦b≦0.5, particularlysuitably 0.01≦b≦0.35.

When element L contains at least one selected from the group consistingof Ti and Nb, the total atom ratio c of Ti and Nb with respect to thetotal of Ni, Co, and element L is suitably 0.001≦c≦0.1, particularlysuitably 0.001≦c≦0.08.

The atom ratio d of Ni with respect to the total of Ni, Co, and elementL is preferably 60≦d≦90, particularly suitably 70≦d≦85.

The atom ratio e of Co with respect to the total of Ni, Co, and elementL is preferably 5≦e≦50, particularly suitably 10≦d≦35.

The Ni/Co lithium composite oxide represented by the above generalformula can be synthesized by sintering a raw material having apredetermined metal element ratio in an oxidizing atmosphere. The rawmaterial includes lithium, nickel (and/or cobalt), and element L. Theraw material includes oxides, hydroxides, oxyhydroxides, carbonates,nitrates, and organic complex salts of each metal element. These may beused either alone or in combination of two or more thereof.

From the viewpoint of facilitating the synthesis of Ni/Co lithiumcomposite oxide, a solid solution containing a plurality of metalelements is preferably used. The solid solution containing a pluralityof metal elements may be any of oxides, hydroxides, oxyhydroxides,carbonates, nitrates, and organic complex salts. For example, a solidsolution containing Ni and Co, a solid solution containing Ni andelement L, a solid solution containing Co and element L, and a solidsolution containing Ni, Co, and element L are preferably used.

Temperature for sintering the raw material and oxygen partial pressurein an oxidizing atmosphere are dependent on the composition and amountof the raw material, and synthesis devices. A person skilled in the artcan select appropriate conditions for them.

Other elements other than Li, Ni, Co, and element L may be mixed inindustrial raw materials as impurities within such amounts that areusually contained therein. However, these impurities do not have largeinfluences on the advantages of the present invention.

Lithium composite oxide is treated with a coupling agent having aplurality of hydrolyzable groups.

The coupling agent has at least one organic functional group and aplurality of hydrolyzable groups in a molecule thereof. The organicfunctional group has various hydrocarbon backbones. The hydrolyzablegroup imparts a hydroxyl group directly bonded to a metal atom (e.g.Si—OH, Ti—OH, and Al—OH) by hydrolysis. Examples of the functional groupinclude alkyl group, mercaptopropyl group, and trifluoropropyl group.Examples of the hydrolyzable group include hydrolyzable alkoxy group andchlorine atom.

In the specification, “treatment with a coupling agent” means thathydroxyl groups (OH group) present on the surface of lithium compositeoxide are brought into reaction with the hydrolyzable groups of thecoupling agent. For example, if the hydrolyzable group is an alkoxygroup (OR group: R is an alkyl group), alcohol elimination reactionproceeds between the alkoxy and hydroxyl groups. In addition, if thehydrolyzable group is a chlorine atom (Cl group), hydrogen chloride(HCl) elimination reaction proceeds between the chlorine atom andhydroxyl groups.

The presence or absence of the treatment with the coupling agent can beconfirmed through the formation of X—O—Si bond (X is the surface oflithium composite oxide), X—O—Ti bond, X—O—Al bond, etc. on the surfaceof a lithium composite oxide. When the lithium composite oxide containsSi, Ti, Al, etc. as element L, Si, Ti, and Al constituting the lithiumcomposite oxide differs in structure from Si, Ti, and Al derived fromthe coupling agent. Thus, they are distinguishable.

As the coupling agent, usable are, for example, a silane coupling agent,aluminate coupling agent, titanate coupling agent. These may be eitheralone or in combination of plural kinds thereof. Among these, a silanecoupling agent is particularly preferable. The silane coupling agent canform an inorganic polymer having siloxane bond as backbone. Coating ofthe surface of the active material with such an inorganic polymerinhibits side reaction. In other words, as a result of the surfacetreatment, the active material particle preferably carries a silicidecompound.

Further, if the reactivity of the active material particle surface withthe hydroxyl group is taken into consideration, the silane couplingagent preferably has as a hydrolyzable group at least one selected fromthe group consisting of alkoxy group and chlorine atom. Furthermore,from the viewpoint of inhibiting the side reaction with electrolyte, thesilane coupling agent preferably has an organic functional groupcomprising at least one kind selected from the group consisting ofmercapto group, alkyl group and fluorine atom.

The amount of coupling agent to be added to lithium composite oxide ispreferably 2% by weight or less, more preferably 0.05 to 1.5% by weight.With respect to the lithium composite oxide If the amount of thecoupling agent to be added exceeds 2% by weight, the surface of activematerial particle may be excessively coated with the coupling agent thatdoes not engage in reaction.

In the present invention, the remaining hydrolyzable groups that havenot been bonded to lithium composite oxide are inactivated. In thiscontext, “inactivation” means that the remaining hydrolyzable groups arebrought into reaction to change to other structure.

For example, at least one kind of hydroxyl group-containing substanceselected from the group consisting of inorganic hydroxide and inorganicoxyhydroxide is imparted to the surface of lithium composite oxide. Theimparted hydroxyl group-containing substance reacts with the remaininghydrolyzable group, thereby inactivating the hydrolyzable group. In thiscase, it is considered that the hydrolyzable group is changed to, forexample, hydroxyl group, peroxide group (OOM: M is a metal element) bythe inactivation.

When hydroxyl group-containing substance is imparted to the surface oflithium composite oxide, for example, an aqueous solution or an organicsolution having hydroxyl group-containing substance dissolved therein isprepared. Then, the lithium composite oxide treated with the couplingagent is dispersed in the obtained solution. Hydroxyl group-containingsubstance may be imparted to lithium composite oxide in advance. In thiscase, the lithium composite oxide that is not treated with the couplingagent is dispersed in an aqueous solution or an organic solution havinghydroxyl group-containing substance dissolved therein, and then dried.Thereafter, a positive electrode is produced using the lithium compositeoxide having hydroxyl group-containing substance, and the obtainedpositive electrode is treated with the coupling agent. The concentrationof hydroxyl group-containing substance in an aqueous solution or anorganic solution having hydroxyl group-containing substance dissolvedtherein is preferably 0.002 to 0.5 mol/L.

As the hydroxyl group-containing substance, usable are, for example,LiOH, NaOH, manganese benzoate, and Mn(OH)₂. These may be used eitheralone or in combination of plural kinds thereof.

The remaining hydrolyzable group can be inactivated by imparting aligating compound having two or more reactive groups to the surface oflithium composite oxide. In this case, the imparted ligating compoundreacts with the remaining hydrolyzable group. Specifically, two or morereactive groups of the ligating compound simultaneously react with twoor more hydrolyzable groups. As a result, the hydrolyzable groups areinactivated. Each of two or more reactive groups of the ligatingcompound is preferably hydroxyl group, carbonyl group, carboxyl group,or alkoxy group. Further, two or more reactive groups are preferably thesame kind of group.

In this invention, the ligating compound is a compound that can form thecoordination compound reacting with the hydrolyzable group of thecoupling agent. Examples of the ligating compound include β-diketone,alkanolamine, α-hydroxyketone, acid anhydrides, and diols. Particularlypreferable are maleic acid, maleic anhydride, ethyl acetoacetate(β-diketone), 2,4-pentadion (β-diketone), triethanol amine(alkanolamine), 2-amino-2-methyl-1-propanol (alkanolamine),4-hydroxy-2-butanone (α-hydroxyketone), 3-hydroxy-2-pentanone(α-hydroxyketone), 1-phenyl-1-oxo-2-hydroxypropane (α-hydroxyketone),phthalic anhydride (acid anhydride), and fumaric anhydride (acidanhydride).

Further, a silylating agent may be imparted to the surface of lithiumcomposite oxide. Preferably, the silylating agent has only one reactivegroup and the remaining group is an organic group with a carbon numberof 5 or less. In this case, the imparted silylating agent reacts withthe remaining hydrolyzable group. As a result, the hydrolyzable group isinactivated. Examples of the reactive group of the silylating agentinclude alkoxy group, chlorine atom, and mercapto group. Further, as theorganic group with a carbon number of 5 or less, preferable are methylgroup, ethyl group, propyl group, and pentyl group. Specific examples ofthe silylating agent include trialkylchlorosilane andtrialkylalkoxysilane.

When a ligating compound or a silylating agent is imparted to thesurface of lithium composite oxide, an aqueous solution or an organicsolution having the ligating compound or the silylating agent dissolvedtherein, for example, is prepared. The lithium composite oxide treatedwith the coupling agent is dispersed in the obtained solution. Theconcentration of the ligating compound or silylating agent in thesolution is preferably 0.01 to 2 mol/L.

Next, one exemplary method for producing a positive electrode isdescribed.

(i) First Step

First, a lithium composite oxide represented by the general formula (1):Li_(x)M_(1-y)L_(y)O₂ is prepared. The method for preparing the lithiumcomposite oxide is not particularly limited. The lithium composite oxidecan be synthesized by, for example, sintering a raw material having apredetermined metal element ratio in an oxidizing atmosphere. Sinteringtemperature, oxygen partial pressure in an oxidizing atmosphere, or thelike may properly be selected depending on the composition and amount ofa raw material, and the synthesis device.

(ii) Second Step

The obtained lithium composite oxide is treated with a coupling agent.The treatment method is not particularly limited. For example, onlyaddition of the coupling agent to the lithium composite oxide issufficient. However, it is preferable to allow the coupling agent toconform to the entire of lithium composite oxide. From this viewpoint,it is desirable to disperse the lithium composite oxide in a solution ora dispersion solution of the coupling agent, and thereafter to remove asolvent. It is preferable to stir the lithium composite oxide, forexample, in the solution or dispersion solution of coupling agent at 20°C. to 40° C. for 5 to 60 minutes.

The solvent for dissolving or dispersing the coupling agent is notparticularly limited, but preferable are: ketones such as dioxane,acetone, and methyl ethyl ketone (MEK); ethers such as tetrahydrofuran(THF); alcohols such as ethanol; N-methyl-2-pyrrolidone (NMP), and thelike. Further, an alkaline water with pH of 10 to 14 is usable.

(iii) Third Step

The lithium composite oxide is immersed in a solution or a dispersionsolution containing a hydroxyl group-containing substance, a ligatingcompound, or a silylating agent. This allows the remaining hydrolyzablegroups to be inactivated.

(iv) Fourth Step

After the inactivation of the remaining hydrolyzable groups of thecoupling agent, a mixture for positive electrode containing activematerial particles, a conductant agent, and a binder is dispersed in aliquid component to prepare a paste. The obtained paste is applied anddried onto a positive electrode core material (current collector forpositive electrode), thereby obtaining a positive electrode. Temperatureand time period for drying after the application of the paste onto thepositive electrode core material are not particularly limited. It issufficient to conduct the drying, for example, at approximately 100° C.for about 10 minutes.

In the lithium composite oxide, it is preferable that element L existsmore abundantly on the surface layer than inside the active materialparticle. For example, the lithium composite oxide before the couplingtreatment is allowed to carry a raw material for element L, and then thelithium composite oxide is sintered.

The sintering is conducted at 650° C. to 750° C. for 2 to 24 hours(preferably about 6 hours) in an oxygen or air atmosphere. In this case,the pressure of the oxygen atmosphere is preferably 10 kPa to 50 kPa. Bythis sintering process, it is possible to obtain an active materialparticle having element L on the surface layer more abundantly than theinside thereof.

As a binder to be included in the mixture for positive electrode, any ofthermoplastic resins and thermosetting resins may be used, butthermoplastic resins are preferable. Examples of thermoplastic resinsusable as a binder include polyethylene, polypropylene,polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrenebutadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer(FEP), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA),vinylidene fluoride-hexafluoropropylene copolymer, vinylidenefluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylenecopolymer (ETFE), polychlorotrifluoroethylene (PCTFE), vinylidenefluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylenecopolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE),vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer,vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylenecopolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acidcopolymer, ethylene-methylacrylate copolymer, andethylene-methylmethacrylate copolymer. These may be used alone or incombination of two or more thereof. These may be used in the form of across-linked material with sodium ion or the like.

As the conductive material to be included in the mixture for positiveelectrode, any electronically conductive material may be used as long asit is chemically stable in a battery. Examples thereof include graphitessuch as natural graphite (scale-shaped graphite or the like) andartificial graphite; carbon blacks such as acetylene black, ketjenblack, channel black, furnace black, lamp black, and thermal black;conductive fiber such as carbon fiber and metal fiber; metallic powderssuch as aluminum; conductive whiskers such as zinc oxide and potassiumtitanate; conductive metal oxide such as titanium oxide; organicconductive materials such as polyphenylene derivative; and carbonfluoride. These may be used alone or in combination of two or morethereof. The amount of the conductive material to be added is notparticularly limited, but it is preferably 1 to 50% by weight, morepreferably 1 to 30% by weight, particularly preferably 2 to 15% byweight with respect to the active material particle contained in themixture for positive electrode.

As the positive electrode core material (current collector for positiveelectrode), any electronically conductive material may be used as longas it is chemically stable in a battery. Usable are foils or sheetscomposed of, for example, aluminum, stainless steel, nickel, titanium,carbon, and conductive resin. Among these, aluminum foil, aluminum alloyfoil, and the like are particularly preferable. On the surface of foilor sheet, a layer of carbon or titanium may be imparted or an oxidelayer may be formed. Irregularities may be imparted to the surface offoil or sheet. The current collector may be used in the form of, forexample, net, punched sheet, lath member, porous member, foam, andmolded article of fibers. The thickness of the positive electrode corematerial is not particularly limited, but within a range of 1 to 500 μm,for example.

The method for treating an active material particle composed of lithiumcomposite oxide has been described above. Next, a method for treating anelectrode plate is described.

(i) First Step

A lithium composite oxide represented by the general formula (1):Li_(x)M_(1-y)L_(y)O₂ is prepared in the same manner in the case oftreating an active material particle composed of lithium composite oxidewith a coupling agent.

(ii) Second Step

The obtained lithium composite oxide is immersed in a solution of ahydroxyl group-containing substance, a ligating compound, or asilylating agent, and thereafter dried. This process allows a hydroxylgroup-containing substance, a ligating compound, or a silylating agentto be attached to the lithium composite oxide.

(iii) Third Step

A mixture for positive electrode containing the obtained active materialparticle, a conductive agent, and a binder is dispersed in a liquidcomponent to prepare a paste. The obtained paste is applied and driedonto a positive electrode core material (current collector for positiveelectrode), thereby obtaining a positive electrode. Temperature and timeperiod for drying after the application of the paste onto the positiveelectrode core material are not particularly limited, but it issufficient to conduct the drying, for example, at approximately 100° C.for about 10 minutes.

The hydroxyl group-containing substance, ligating compound, orsilylating agent may be added to a paste before the paste is appliedonto the positive electrode core material. In this case, second step canbe omitted.

(iv) Fourth Step

The positive electrode containing the hydroxyl group-containingsubstance, ligating compound, or silylating agent is treated with acoupling agent. A treatment method is not particularly limited. Forexample, the positive electrode is immersed in a coupling agent for 5 to10 minutes, and then dried at 110° C. for about 10 minutes. However, itis preferable to allow the coupling agent to conform to the entire oflithium composite oxide. From this viewpoint, it is desirable to use asolution or dispersion solution containing the coupling agent.

The solvent for dissolving or dispersing the coupling agent is notparticularly limited, but preferable are: ketones such as dioxane,acetone, and methyl ethyl ketone (MEK); ethers such as tetrahydrofuran(THF); alcohols such as ethanol; N-methyl-2-pyrrolidone (NMP), and thelike. Further, an alkaline water with pH of 10 to 14 is usable.

In the case for allowing element L to exist more abundantly on thesurface layer than inside the active material particle, the activematerial particle is prepared in the same manner as in the case fortreating the active material particle with the coupling agent.

As the binder, conductive material, and positive electrode core material(current collector for positive electrode), materials that are describedfor the case for treating the active material particle with the couplingagent can be used.

Hereafter, constituent elements other than positive electrode of thelithium ion secondary battery of the present invention are described.However, the lithium ion secondary battery has a feature of includingthe above-described positive electrode, and the other constituentelements are not particularly limited. Therefore, the followingdescriptions do not restrict the present invention.

As a lithium-chargeable and dischargeable negative electrode, a negativeelectrode core material carrying a mixture for negative electrode can beused. The mixture for negative electrode includes, for example, anegative electrode active material and a binder, and as an optionalcomponent, includes a conductive material and a thickener. A negativeelectrode of this kind can be produced in the same manner as thepositive electrode.

The negative electrode active material may be a material that canelectrochemically charge and discharge lithium. For example, graphite,hard-to-graphitize carbon materials, lithium alloys, metal oxides, andthe like can be used. The lithium alloy is preferably an alloycontaining at least one selected from the group consisting of silicon,tin, aluminum, zinc, and magnesium. The metal oxide is preferably asilicon-containing oxide or a tin-containing oxide, and it is morepreferable that the metal oxide is hybridized with a carbon material.The average particle size of the negative electrode active material isnot particularly limited, but is preferably 1 to 30 μm.

As a binder to be included in the mixture for negative electrode, any ofthermoplastic resins and thermosetting resins may be used, butthermoplastic resins are preferable. Examples of thermoplastic resinsusable as a binder include polyethylene, polypropylene,polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrenebutadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer(FEP), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA),vinylidene fluoride-hexafluoropropylene copolymer, vinylidenefluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylenecopolymer (ETFE), polychlorotrifluoroethylene (PCTFE), vinylidenefluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylenecopolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE),vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer,vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylenecopolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acidcopolymer, ethylene-methyl acrylate copolymer, and ethylene-methylmethacrylate copolymer. These may be used alone or in combination of twoor more thereof. These may be used in the form of a cross-linkedmaterial with sodium ion or the like.

As the conductive material to be included in the mixture for negativeelectrode, any electronically conductive material may be used as long asit is chemically stable in a battery. Examples thereof include graphitessuch as natural graphite (scale-shaped graphite or the like) andartificial graphite; carbon blacks such as acetylene black, ketjenblack, channel black, furnace black, lamp black, and thermal black;conductive fiber such as carbon fiber and metal fiber; metallic powderssuch as copper and nickel; and organic conductive materials such aspolyphenylene derivative. These may be used alone or in combination oftwo or more thereof. The amount of the conductive material to be addedis not particularly limited, but it is preferably 1 to 30% by weight,more preferably 1 to 10% by weight with respect to the active materialparticle contained in the mixture for negative electrode.

As the negative electrode core material (current collector for negativeelectrode), any electronically conductive material may be used as longas it is chemically stable in a battery. Usable are foils or sheetscomposed of, for example, stainless steel, nickel, copper, titanium,carbon, and conductive resin. Among these, copper foil, copper alloyfoil, and the like are particularly preferable. On the surface of foilor sheet, a layer of carbon, titanium, or nickel may be imparted or anoxide layer may be formed. Irregularities may be imparted to the surfaceof foil or sheet. The current collector may be used in the form of, forexample, net, punched sheet, lath member, porous member, foam, andmolded article of fibers. The thickness of the negative electrode corematerial is not particularly limited, but within a range of 1 to 500 μm,for example.

As a non-aqueous electrolyte, preferably used is a non-aqueous solventhaving a lithium salt dissolved therein.

Examples of the solvent include cyclic carbonates such as ethylenecarbonate (EC), propylene carbonate (PC), and butylene carbonate (BC);chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate(DEC), ethylmethyl carbonate (EMC), and dipropyl carbonate (DPC);aliphatic carboxylic acid esters such as methyl formate, methyl acetate,methyl propionate, and ethyl propionate; lactones such asγ-butyrolactone and γ-valerolactone; chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxy ethane (DEE), and ethoxymethoxy ethane (EME);cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran;dimethyl sulfoxide; 1,3-dioxolane; formamide; acetamide;dimethylformamide; dioxolane; acetonitrile; propylnitrile; nitromethane;ethyl monoglyme; phosphate trimester; trimethoxy methane; dioxolanederivative; sulfolane; methyl sulfolane; 1,3-dimethyl-2-imidazolidinone;3-methyl-2-oxazolidinone; propylene carbonate derivative;tetrahydrofuran derivative; ethyl ether; 1,3-propanesultone; anisole;dimethyl sulfoxide; or N-methyl-2-pyrrolidone. These may be used alonebut preferably two or more thereof may be mixed for use. Among these,preferable is a mixture solvent of a cyclic carbonate and a chaincarbonate, or a mixture solvent of a cyclic carbonate, a chaincarbonate, and an aliphatic carboxylic acid ester.

Examples of the lithium salt to be dissolved in the non-aqueous solventinclude LiClO₄, LiBF₄, LiPF₆, LiAlCl₄, LiSbF₆, LiSCN, LiCl, LiCF₃SO₃,LiCF₃CO₂, Li(CF₃SO₂)₂, LiAsF₆, LiN(CF₃SO₂)₂, LiB₁₀Cl₁₀, lithium loweraliphatic carbonate, LiBr, LiI, LiBCl₄, lithium tetraphenylborate, andlithium imide salts. These may be used either alone or in combination oftwo or more thereof. However, at least LiPF₆ is preferably used. Thedissolution amount of the lithium salt with respect to the non-aqueoussolvent is not particularly limited, but the concentration of lithiumsalt is preferably 0.2 to 2 mol/L, more preferably 0.5 to 1.5 mol/L.

For the purpose of improving charge-discharge properties of a battery,various additives can be added to the non-aqueous electrolyte. Examplesof the additive include triethylphosphate, triethanolamine, cyclicethers, ethylenediamine, n-glyme, pyridine, hexaphosphate triamide,nitrobenzene derivatives, crown ethers, quaternary ammonium salts, andethylene glycol dialkylether.

From the viewpoint of improving intermittent cycle properties, at leastone additive selected from the group consisting of vinylene carbonate,vinylethylene carbonate, phosphazene, and fluorobenzene is preferablyadded to the non aqueous electrolyte. An appropriate content of theseadditives is 0.5 to 10% by weight of the non-aqueous electrolyte.

It is necessary to dispose a separator between the positive and negativeelectrodes. As the separator, an insulating fine porous thin film havinghigh ion permeability and predetermined mechanical strength ispreferably used. It is preferable that the separator has a function toclose pores at a predetermined temperature or higher to increaseresistance. As a material for the fine porous thin film, preferably usedis polyolefin such as polypropylene and polyethylene, which hasexcellent resistance to organic solvents and hydrophobicity. A sheet, anonwoven cloth, a woven cloth, and the like made of glass fiber are alsoused. The separator has a pore diameter of 0.01 to 1 μm, for example.The separator generally has a thickness of 10 to 300 μm. The separatorgenerally has a porosity of 30 to 80%.

Instead of the separator, a non-aqueous electrolyte and a polymermaterial (polymer electrolyte) holding the electrolyte can be used. Inthis case, the polymer electrolyte is used integrally with the positiveor negative electrode. As long as the polymer material can hold thenon-aqueous electrolyte, any polymer material is usable, but a copolymerof vinylidene fluoride and hexafluoropropylene is particularlypreferable.

Next, the present invention will be described in detail based onExamples, but the present invention is not limited to the followingExamples.

EXAMPLE 1

Battery A1

(i) Synthesis of Lithium Composite Oxide

A mixture of nickel sulfate, cobalt sulfate, and aluminum sulfate wasprepared such that a molar ratio of Ni atom, Co atom, and Al atom is80:15:5, and 3 kg of the mixture was dissolved in 10 L of water,obtaining a raw material solution. To the raw material solution, 400 gof sodium oxide was added to produce a precipitate. The precipitate waswell washed with water and dried to obtain a co-precipitated hydroxide.A predetermined amount of lithium hydroxide was mixed with 3 kg of theobtained Ni—Co—Al co-precipitated hydroxide, and sintered in anatmosphere with an oxygen partial pressure of 0.5 atmospheric pressureat a synthesis temperature of 750° C. for 10 hours to obtain a Ni/Colithium composite oxide containing Al as element L(LiNi_(0.8)Co_(0.15)Al_(0.05)O₂).

(ii) Synthesis of Active Material Particle

The obtained composite oxide was treated with a coupling agent, andthereafter with a LiOH aqueous solution. Specifically, 2 kg of Ni/Colithium composite oxide and 0.5% by weight of3-mercaptopropyltrimethoxysilane with respect to the Ni/Co lithiumcomposite oxide were inputted into 10 L of dehydrated dioxane, and theobtained dispersion solution was stirred at 25° C. for 3 hours. Then, 2L of 0.2% by weight of LiOH aqueous solution was added to the dispersionsolution, and further stirred at 25° C. for 2 hours. Thereafter, thecomposite oxide was filtrated, washed well with acetone, and dried at100° C. for 2 hours.

In the obtained active material particle, the remaining hydrolyzablegroup (methoxy group) of the coupling agent is considered to beinactivated by reaction with LiOH added as a stabilizer.

(iii) Production of Positive Electrode

1 kg of the obtained active material particles (average particlediameter 12 μm), 0.5 kg of PVDF #1320 (a solution ofN-methyl-2-pyrrolidone (NMP) with a solid content of 12% by weight)available from Kureha Chemical Industry Co., Ltd., 40 g of acetyleneblack, and an appropriate amount of NMP were stirred with a double-armkneader to prepare a mixture paste for positive electrode. This pastewas applied onto both sides of an aluminum foil with a thickness of a 20μm (positive electrode core material), and dried. After drying, theobtained foil was rolled so as to have a total thickness of 160 μm.Thereafter, the obtained electrode plate was slit to have such a widththat it could be inserted into a 18650 cylindrical battery case,obtaining a positive electrode.

(iv) Production of Negative Electrode

3 kg of artificial graphite, 200 g of BM-400B available from ZeonCorporation (a dispersion solution of modified styrene-butadiene rubberwith a solid content of 40% by weight), 50 g of carboxymethyl cellulose(CMC), and an appropriate amount of water were stirred with a double-armkneader to prepare a mixture paste for negative electrode. This pastewas applied to onto both sides of a copper foil with a thickness of 12μm (negative electrode core material), dried, and rolled so as to have atotal thickness of 160 μm. Thereafter, the obtained electrode plate wasslit to have such a width that it could be inserted into a 18650cylindrical battery case, obtaining a negative electrode.

(v) Preparation of Non-Aqueous Electrolyte

A mixed solvent of ethylene carbonate and methyl ethyl carbonate wasprepared at a capacity ratio of 10:30. To the mixed solvent, 2% byweight of vinylene carbonate, 2% by weight of vinylethylene carbonate,5% by weight of fluorobenzene, and 5% by weight of phosphazene wereadded, obtaining a mixed solution. LiPF₆ was dissolved in this mixedsolution at a concentration of 1.5 mol/L, obtaining a non-aqueouselectrolyte.

(vi) Assembly of Battery

As shown in the FIGURE, a positive electrode 5 and a negative electrode6 were wound via a separator 7 to form a group of electrode plates witha spiral shape. As the separator 7, a composite film of polyethylene andpolypropylene (2300 available from Celgard Inc. with a thickness of 25μm) was used.

A positive lead 5 a and a negative lead 6 a both made of nickel wereattached to the positive and negative electrodes 5 and 6, respectively.This group of electrode plates has an upper insulating plate 8 a and alower insulating plate 8 b arranged on upper and lower faces thereof,and inserted into a battery case 1. Further, 5 g of the non-aqueouselectrolyte was injected in the battery case 1.

Thereafter, a sealing plate 2 with an insulating gasket 3 arrangedtherearound and the positive electrode lead 5 a were brought intoconduction, and an opening of the battery case 1 was sealed with thesealing plate 2. Accordingly, a 18650 cylindrical lithium ion secondarybattery (design capacity: 2000 mAh) was completed. This battery was usedas an example Battery A1.

Battery A2

A lithium ion secondary battery was produced in the same manner as inBattery A1 except that an aqueous solution with 0.2% by weight of NaOHwas used to inactivate the remaining hydrolyzable group of the couplingagent instead of an aqueous solution with 0.2% by weight of LiOH.

Battery A3

A lithium ion secondary battery was produced in the same manner as inBattery A1 except that an aqueous solution with 0.2% by weight of KOHwas used to inactivate the remaining hydrolyzable group of the couplingagent instead of an aqueous solution with 0.2% by weight of LiOH.

Battery A4

A lithium ion secondary battery was produced in the same manner as inBattery A1 except that composite oxide having been treated with acoupling agent was treated with ethyl acetoacetate (β-diketone) toinactivate the remaining hydrolyzable group. Specifically, 2 kg of Ni/Colithium composite oxide and 0.5% by weight of3-mercaptopropyltrimethoxysilane with respect to Ni/Co lithium compositeoxide were inputted into 10 L of dehydrated dioxane, and the obtaineddispersion solution was stirred at 25° C. for 3 hours. Then, 0.2% byweight of ethyl acetoacetate with respect to the composite oxide wasadded to the dispersion solution, and further stirred at 25° C. for 2hours, thereby inactivating the remaining hydrolyzable group.Thereafter, the composite oxdies were filtrated, washed with acetone,and dried at 100° C. for 2 hours.

Battery A5

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that 2,4-pentadion(β-diketone) was used to inactivatethe remaining hydrolyzable group of the coupling agent instead of ethylacetoacetate.

Battery A6

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that triethanol amine(alkanolamine) was used toinactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

Battery A7

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that 2-amino-2-methyl-1-propanol(alkanolamine) wasused to inactivate the remaining hydrolyzable group of the couplingagent instead of ethyl acetoacetate.

Battery A8

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that 4-hydroxy-2-butanone(α-hydroxyketone) was used toinactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

Battery A9

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that 3-hydroxy-2-pentanone(α-hydroxyketone) was usedto inactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

Battery A10

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that 1-phenyl-1-oxo-2-hydroxypropane(α-hydroxyketone)was used to inactivate the remaining hydrolyzable group of the couplingagent instead of ethyl acetoacetate.

Battery A11

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that maleic anhydride (acid anhydride) was used toinactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

Battery A12

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that phthalic anhydride (acid anhydride) was used toinactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

Battery A13

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that fumaric anhydride (acid anhydride) was used toinactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

Battery A14

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that trimethylchlorosilane (silylating agent) was usedto inactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

Battery A15

A lithium ion secondary battery was produced in the same manner as inBattery A4 except that tripentylchlorosilane (silylating agent) was usedto inactivate the remaining hydrolyzable group of the coupling agentinstead of ethyl acetoacetate.

[Evaluation 1]

(Discharge Characteristic)

Pre-conditioning charge and discharge were conducted for each battery,followed by storage for 2 days under an environment at 40° C.Thereafter, each battery was subjected to the following two patterns ofcycle tests. Here, the design capacity of the battery was 1 CmAh.

First Pattern (Ordinary Cycle Test)

(1) constant current charge (45° C.): 0.7 CmA (cut-off voltage 4.2 V)

(2) constant voltage charge (45° C.): 4.2 V (cut-off current 0.05 CmA)

(3) charge rest (45° C.): 30 minutes

(4) constant current discharge (45° C.): 1 CmA (cut-off voltage 2.5 V)

(5) discharge rest (45° C.): 30 minutes

Second Pattern (Intermittent Cycle Test)

(1) constant current charge (45° C.): 0.7 CmA (cut-off voltage 4.2 V)

(2) constant voltage charge (45° C.): 4.2 V (cut-off current 0.05 CmA)

(3) charge rest (45° C.): 720 minutes

(4) constant current discharge (45° C.): 1 CmA (cut-off voltage 2.5 V)

(5) discharge rest (45° C.): 720 minutes

Discharge capacities obtained after 500 cycles of first and secondpatterns were shown in Tables 1 to 22.

TABLE 1 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example A1 3-mercaptopropyl- LiOH aqueoussolution 2001 1500 Example A2 trimethoxysilane NaOH aqueous solution2000 1502 Example A3 KOH aqueous solution 1999 1505 Example A4 ethylacetoacetate (β-diketone) 2000 1499 Example A5 2,4-pentadion(β-diketone) 2001 1502 Example A6 triethanol amine 2002 1500 Example A72-amino-2-methyl-1-propanol 2003 1498 Example A8 4-hydroxy-2-butanone1999 1499 Example A9 3-hydroxy-2-pentanone 2001 1500 Example A101-phenyl-1-oxo-2-hydroxypropane 2000 1497 Example A11 maleic anhydride(acid anhydride) 2002 1497 Example A12 phthalic anhydride (acidanhydride) 2002 1502 Example A13 fumaric anhydride (acid anhydride) 20001502 Example A14 trimethylchlorosilane (silylating agent) 2001 1499Example A15 tripentylchlorosilane (silylating agent) 1999 1502Comparative none 2002  802 Example A1

EXAMPLE 2

Batteries B1 to B15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3-methacryloxypropyltrimethoxysilane was used as a coupling agentinstead of 3-mercaptopropyltrimethoxysilane. The results are shown inTable 2.

TABLE 2 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example B1 3-methacryloxypropyl- LiOH aqueoussolution 2001 1500 Example B2 trimethoxysilane NaOH aqueous solution2002 1500 Example B3 KOH aqueous solution 2001 1502 Example B4 ethylacetoacetate (β-diketone) 1999 1503 Example B5 2,4-pentadion(β-diketone) 2000 1499 Example B6 triethanol amine 2001 1498 Example B72-amino-2-methyl-1-propanol 2001 1497 Example B8 4-hydroxy-2-butanone2002 1500 Example B9 3-hydroxy-2-pentanone 2000 1510 Example B101-phenyl-1-oxo-2-hydroxypropane 1999 1509 Example B11 maleic anhydride(acid anhydride) 1998 1508 Example B12 phthalic anhydride (acidanhydride) 1997 1507 Example B13 fumaric anhydride (acid anhydride) 20001500 Example B14 trimethylchlorosilane (silylating agent) 2001 1503Example B15 tripentylchlorosilane (silylating agent) 2002 1505Comparative none 2001  800 Example B1

EXAMPLE 3

Batteries C1 to C15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3,3,3-trifluoropropyltrichlorosilane was used as a coupling agentinstead of 3-mercaptopropyltrimethoxysilane. The results are shown inTable 3.

TABLE 3 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example C1 3,3,3- LiOH aqueous solution 2003 1501Example C2 trifluoropropyl- NaOH aqueous solution 2000 1502 Example C3trichlorosilane KOH aqueous solution 1999 1508 Example C4 ethylacetoacetate (β-diketone) 2000 1510 Example C5 2,4-pentadion(β-diketone) 2001 1509 Example C6 triethanol amine 1999 1502 Example C72-amino-2-methyl-1-propanol 1998 1501 Example C8 4-hydroxy-2-butanone2000 1504 Example C9 3-hydroxy-2-pentanone 2001 1505 Example C101-phenyl-1-oxo-2-hydroxypropane 2002 1507 Example C11 maleic anhydride(acid anhydride) 2003 1508 Example C12 phthalic anhydride (acidanhydride) 2000 1509 Example C13 fumaric anhydride (acid anhydride) 19991502 Example C14 trimethylchlorosilane (silylating agent) 1998 1500Example C15 tripentylchlorosilane (silylating agent) 1999 1508Comparative none 2000  801 Example C1

EXAMPLE 4

Batteries D1 to D15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3,3,4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane was used as a couplingagent instead of 3-mercaptopropyl-trimethoxysilane. The results areshown in Table 4.

TABLE 4 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example D1 3,3,4,4,5,5,6,6,6- LiOH aqueoussolution 1999 1502 Example D2 nonafluorohexyl- NaOH aqueous solution2001 1507 Example D3 trichlorosilane KOH aqueous solution 1997 1500Example D4 ethyl acetoacetate (β-diketone) 1997 1507 Example D52,4-pentadion (β-diketone) 2002 1500 Example D6 triethanol amine 19991503 Example D7 2-amino-2-methyl-1-propanol 2000 1504 Example D84-hydroxy-2-butanone 2001 1503 Example D9 3-hydroxy-2-pentanone 20021500 Example D10 1-phenyl-1-oxo-2-hydroxypropane 1999 1508 Example D11maleic anhydride (acid anhydride) 1998 1508 Example D12 phthalicanhydride (acid anhydride) 2000 1503 Example D13 fumaric anhydride (acidanhydride) 2001 1509 Example D14 trimethylchlorosilane (silylatingagent) 2003 1508 Example D15 tripentylchlorosilane (silylating agent)2001 1509 Comparative none 2000  799 Example D1

EXAMPLE 5

Batteries E1 to E15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3,3,3-trifluoropropyltrimethoxysilane was used as a coupling agentinstead of 3-mercaptopropyltrimethoxysilane. The results are shown inTable 5.

TABLE 5 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example E1 3,3,3-trifluoropropyl- LiOH aqueoussolution 2003 1501 Example E2 trimethoxysilane NaOH aqueous solution1999 1503 Example E3 KOH aqueous solution 2001 1502 Example E4 ethylacetoacetate (β-diketone) 2000 1502 Example E5 2,4-pentadion(β-diketone) 2001 1500 Example E6 triethanol amine 2000 1500 Example E72-amino-2-methyl-1-propanol 2001 1500 Example E8 4-hydroxy-2-butanone1999 1507 Example E9 3-hydroxy-2-pentanone 2001 1503 Example E101-phenyl-1-oxo-2-hydroxypropane 1999 1508 Example E11 maleic anhydride(acid anhydride) 2001 1497 Example E12 phthalic anhydride (acidanhydride) 2002 1507 Example E13 fumaric anhydride (acid anhydride) 20001509 Example E14 trimethylchlorosilane (silylating agent) 1998 1500Example E15 tripentylchlorosilane (silylating agent) 2000 1510Comparative none 1999  800 Example E1

EXAMPLE 6

Batteries F1 to F15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that hexyltrimethoxysilane wasused as a coupling agent instead of 3-mercaptopropyltrimethoxysilane.The results are shown in Table 6.

TABLE 6 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example F1 hexyl- LiOH aqueous solution 1999 1502Example F2 trimethoxysilane NaOH aqueous solution 1999 1508 Example F3KOH aqueous solution 2002 1500 Example F4 ethyl acetoacetate(β-diketone) 1998 1508 Example F5 2,4-pentadion (β-diketone) 2003 1501Example F6 triethanol amine 2002 1500 Example F72-amino-2-methyl-1-propanol 2001 1505 Example F8 4-hydroxy-2-butanone2001 1497 Example F9 3-hydroxy-2-pentanone 1998 1501 Example F101-phenyl-1-oxo-2-hydroxypropane 2001 1503 Example F11 maleic anhydride(acid anhydride) 2001 1500 Example F12 phthalic anhydride (acidanhydride) 2003 1508 Example F13 fumaric anhydride (acid anhydride) 19991503 Example F14 trimethylchlorosilane (silylating agent) 2000 1510Example F15 tripentylchlorosilane (silylating agent) 2000 1503Comparative none 2002  800 Example F1

EXAMPLE 7

Batteries G1 to G15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that decyltrichlorosilane wasused as a coupling agent instead of 3-mercaptopropyltrimethoxysilane.The results are shown in Table 7.

TABLE 7 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example G1 decyltrichlorosilane LiOH aqueoussolution 2001 1503 Example G2 NaOH aqueous solution 2000 1507 Example G3KOH aqueous solution 2000 1510 Example G4 ethyl acetoacetate(β-diketone) 1999 1509 Example G5 2,4-pentadion (β-diketone) 2000 1509Example G6 triethanol amine 1997 1500 Example G72-amino-2-methyl-1-propanol 1998 1502 Example G8 4-hydroxy-2-butanone1999 1502 Example G9 3-hydroxy-2-pentanone 2002 1500 Example G101-phenyl-1-oxo-2-hydroxypropane 2000 1503 Example G11 maleic anhydride(acid anhydride) 2001 1502 Example G12 phthalic anhydride (acidanhydride) 2001 1498 Example G13 fumaric anhydride (acid anhydride) 19981500 Example G14 trimethylchlorosilane (silylating agent) 1999 1507Example G15 tripentylchlorosilane (silylating agent) 1999 1508Comparative none 2001  800 Example G1

EXAMPLE 8

Batteries H1 to H15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that6-triethoxysilyl-2-norbornane was used as a coupling agent instead of3-mercaptopropyltrimethoxysilane. The results are shown in Table 8.

TABLE 8 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example H1 6-triethoxysilyl-2- LiOH aqueoussolution 1998 1501 Example H2 norbornene NaOH aqueous solution 2000 1503Example H3 KOH aqueous solution 1999 1503 Example H4 ethyl acetoacetate(β-diketone) 1999 1508 Example H5 2,4-pentadion (β-diketone) 2002 1500Example H6 triethanol amine 2001 1503 Example H72-amino-2-methyl-1-propanol 2000 1500 Example H8 4-hydroxy-2-butanone1999 1502 Example H9 3-hydroxy-2-pentanone 2002 1500 Example H101-phenyl-1-oxo-2-hydroxypropane 2000 1504 Example H11 maleic anhydride(acid anhydride) 2001 1500 Example H12 phthalic anhydride (acidanhydride) 1999 1503 Example H13 fumaric anhydride (acid anhydride) 20001510 Example H14 trimethylchlorosilane (silylating agent) 2001 1498Example H15 tripentylchlorosilane (silylating agent) 2000 1509Comparative none 2001  798 Example H1

EXAMPLE 9

Batteries I1 to I15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3-methacryloxypropyltrimethoxysilane was used as a coupling agentinstead of 3-mercaptopropyltrimethoxysilane. The results are shown inTable 9.

TABLE 9 Intermittent cycle characteristic Charge/ Charge/ Discharge restDischarge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C. Couplingagent Stabilizer (mAh) Example I1 3- LiOH aqueous solution 2002 1500Example I2 methacryloxypropyl- NaOH aqueous solution 2001 1497 ExampleI3 trimethoxysilane KOH aqueous solution 1999 1502 Example I4 ethylacetoacetate (β-diketone) 2001 1509 Example I5 2,4-pentadion(β-diketone) 2001 1502 Example I6 triethanol amine 1997 1500 Example I72-amino-2-methyl-1-propanol 2002 1507 Example I8 4-hydroxy-2-butanone2000 1507 Example I9 3-hydroxy-2-pentanone 1998 1500 Example I101-phenyl-1-oxo-2-hydroxypropane 1998 1502 Example I11 maleic anhydride(acid anhydride) 1997 1507 Example I12 phthalic anhydride (acidanhydride) 2001 1509 Example I13 fumaric anhydride (acid anhydride) 20031501 Example I14 trimethylchlorosilane (silylating agent) 1999 1509Example I15 tripentylchlorosilane (silylating agent) 2002 1505Comparative none 2001  799 Example I1

EXAMPLE 10

Batteries J1 to J15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that dodecyltriethoxysilane wasused as a coupling agent instead of 3-mercaptopropyltrimethoxysilane.The results are shown in Table 10.

TABLE 10 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example J1 dodecyl- LiOH aqueoussolution 2000 1500 Example J2 triethoxysilane NaOH aqueous solution 20001507 Example J3 KOH aqueous solution 1997 1500 Example J4 ethylacetoacetate (β-diketone) 1999 1508 Example J5 2,4-pentadion(β-diketone) 2002 1500 Example J6 triethanol amine 1999 1508 Example J72-amino-2-methyl-1-propanol 1997 1507 Example J8 4-hydroxy-2-butanone2001 1505 Example J9 3-hydroxy-2-pentanone 2001 1503 Example J101-phenyl-1-oxo-2-hydroxypropane 2002 1505 Example J11 maleic anhydride(acid anhydride) 1998 1508 Example J12 phthalic anhydride (acidanhydride) 2003 1501 Example J13 fumaric anhydride (acid anhydride) 19991503 Example J14 trimethylchlorosilane (silylating agent) 2000 1509Example J15 tripentylchlorosilane (silylating agent) 2000 1510Comparative none 2000  795 Example J1

EXAMPLE 11

Batteries K1 to K15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that dimethoxymethylchlorosilanewas used as a coupling agent instead of3-mercaptopropyltrimethoxysilane. The results are shown in Table 11.

TABLE 11 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example K1 Dimethoxymethyl- LiOH aqueoussolution 2002 1500 Example K2 chlorosilane NaOH aqueous solution 20001503 Example K3 KOH aqueous solution 2001 1500 Example K4 ethylacetoacetate (β-diketone) 1999 1502 Example K5 2,4-pentadion(β-diketone) 2000 1504 Example K6 triethanol amine 2001 1509 Example K72-amino-2-methyl-1-propanol 2001 1502 Example K8 4-hydroxy-2-butanone2001 1503 Example K9 3-hydroxy-2-pentanone 1999 1503 Example K101-phenyl-1-oxo-2-hydroxypropane 1999 1509 Example K11 maleic anhydride(acid anhydride) 2001 1500 Example K12 phthalic anhydride (acidanhydride) 2002 1507 Example K13 fumaric anhydride (acid anhydride) 19981501 Example K14 trimethylchlorosilane (silylating agent) 2003 1508Example K15 tripentylchlorosilane (silylating agent) 2001 1507Comparative none 2002  800 Example K1

EXAMPLE 12

Batteries L1 to L15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3-mercaptopropylmethyldimethoxysilane was used as a coupling agentinstead of 3-mercaptopropyltrimethoxysilane. The results are shown inTable 12.

TABLE 12 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example L1 3-mercaptopropyl- LiOHaqueous solution 1999 1502 Example L2 methyldimethoxy- NaOH aqueoussolution 2000 1510 Example L3 silane KOH aqueous solution 2002 1505Example L4 ethyl acetoacetate (β-diketone) 1997 1507 Example L52,4-pentadion (β-diketone) 2002 1500 Example L6 triethanol amine 20001504 Example L7 2-amino-2-methyl-1-propanol 2003 1508 Example L84-hydroxy-2-butanone 2002 1500 Example L9 3-hydroxy-2-pentanone 19981501 Example L10 1-phenyl-1-oxo-2-hydroxypropane 2001 1503 Example L11maleic anhydride (acid anhydride) 1998 1508 Example L12 phthalicanhydride (acid anhydride) 1997 1500 Example L13 fumaric anhydride (acidanhydride) 1999 1507 Example L14 trimethylchlorosilane (silylatingagent) 1999 1508 Example L15 tripentylchlorosilane (silylating agent)1998 1500 Comparative none 2001  802 Example L1

EXAMPLE 13

Batteries M1 to M15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3,3,3-trifluoropropylmethyldichlorosilane was used as a coupling agentinstead of 3-mercaptopropyltrimethoxysilane. The results are shown inTable 13.

TABLE 13 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example M1 3,3,3-trifluoropropyl- LiOHaqueous solution 1999 1509 Example M2 methyldichlorosilane NaOH aqueoussolution 2001 1497 Example M3 KOH aqueous solution 2000 1507 Example M4ethyl acetoacetate (β-diketone) 2001 1507 Example M5 2,4-pentadion(β-diketone) 1999 1503 Example M6 triethanol amine 1999 1502 Example M72-amino-2-methyl-1-propanol 2001 1498 Example M8 4-hydroxy-2-butanone2001 1500 Example M9 3-hydroxy-2-pentanone 2000 1500 Example M101-phenyl-1-oxo-2-hydroxypropane 2002 1507 Example M11 maleic anhydride(acid anhydride) 2000 1502 Example M12 phthalic anhydride (acidanhydride) 2003 1501 Example M13 fumaric anhydride (acid anhydride) 19981502 Example M14 trimethylchlorosilane (silylating agent) 2001 1509Example M15 tripentylchlorosilane (silylating agent) 2000 1510Comparative none 2001  800 Example M1

EXAMPLE 14

Batteries N1 to N15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that diethoxydichlorosilane wasused as a coupling agent instead of 3-mercaptopropyltrimethoxysilane.The results are shown in Table 14.

TABLE 14 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example N1 diethoxy- LiOH aqueoussolution 2002 1507 Example N2 dichlorosilane NaOH aqueous solution 20031508 Example N3 KOH aqueous solution 2000 1509 Example N4 ethylacetoacetate (β-diketone) 1998 1500 Example N5 2,4-pentadion(β-diketone) 2000 1503 Example N6 triethanol amine 1999 1503 Example N72-amino-2-methyl-1-propanol 2001 1502 Example N8 4-hydroxy-2-butanone1999 1508 Example N9 3-hydroxy-2-pentanone 1998 1508 Example N101-phenyl-1-oxo-2-hydroxypropane 2001 1505 Example N11 maleic anhydride(acid anhydride) 2001 1498 Example N12 phthalic anhydride (acidanhydride) 1999 1509 Example N13 fumaric anhydride (acid anhydride) 20021505 Example N14 trimethylchlorosilane (silylating agent) 2001 1503Example N15 tripentylchlorosilane (silylating agent) 1997 1507Comparative none 2001  797 Example N1

EXAMPLE 15

Batteries O1 to O15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that3,3,3-trifluoropropylmethyldimethoxysilane was used as a coupling agentinstead of 3-mercaptopropyltrimethoxysilane. The results are shown inTable 15.

TABLE 15 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example O1 3,3,3-trifluoropropyl- LiOHaqueous solution 2001 1509 Example O2 methyldimethoxy- NaOH aqueoussolution 1999 1507 Example O3 silane KOH aqueous solution 2000 1503Example O4 ethyl acetoacetate (β-diketone) 1997 1500 Example O52,4-pentadion (β-diketone) 2000 1500 Example O6 triethanol amine 20001504 Example O7 2-amino-2-methyl-1-propanol 2000 1499 Example O84-hydroxy-2-butanone 2002 1500 Example O9 3-hydroxy-2-pentanone 19991503 Example O10 1-phenyl-1-oxo-2-hydroxypropane 1999 1502 Example O11maleic anhydride (acid anhydride) 1998 1501 Example O12 phthalicanhydride (acid anhydride) 2001 1509 Example O13 fumaric anhydride (acidanhydride) 2000 1510 Example O14 trimethylchlorosilane (silylatingagent) 2002 1500 Example O15 tripentylchlorosilane (silylating agent)2000 1510 Comparative none 2002  800 Example O1

EXAMPLE 16

Batteries P1 to P15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane was used as a couplingagent instead of 3-mercaptopropyltrimethoxysilane. The results are shownin Table 16.

TABLE 16 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example P1 2-(3,4- LiOH aqueous solution2001 1507 Example P2 epoxycyclohexyl)- NaOH aqueous solution 2002 1500Example P3 ethyltrimethoxysilane KOH aqueous solution 2002 1507 ExampleP4 ethyl acetoacetate (β-diketone) 1997 1507 Example P5 2,4-pentadion(β-diketone) 2003 1501 Example P6 triethanol amine 2001 1505 Example P72-amino-2-methyl-1-propanol 2001 1500 Example P8 4-hydroxy-2-butanone2002 1500 Example P9 3-hydroxy-2-pentanone 2001 1503 Example P101-phenyl-1-oxo-2-hydroxypropane 2000 1503 Example P11 maleic anhydride(acid anhydride) 2001 1498 Example P12 phthalic anhydride (acidanhydride) 2000 1510 Example P13 fumaric anhydride (acid anhydride) 19991503 Example P14 trimethylchlorosilane (silylating agent) 2000 1504Example P15 tripentylchlorosilane (silylating agent) 2001 1509Comparative none 2001  798 Example P1

EXAMPLE 17

Batteries Q1 to Q15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that docosylmethyldichlorosilanewas used as a coupling agent instead of3-mercaptopropyltrimethoxysilane. The results are shown in Table 17.

TABLE 17 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example Q1 docosylmethyl- LiOH aqueoussolution 1999 1503 Example Q2 dichlorosilane NaOH aqueous solution 20011500 Example Q3 KOH aqueous solution 2001 1497 Example Q4 ethylacetoacetate (β-diketone) 2000 1503 Example Q5 2,4-pentadion(β-diketone) 1998 1508 Example Q6 triethanol amine 2002 1505 Example Q72-amino-2-methyl-1-propanol 2000 1510 Example Q8 4-hydroxy-2-butanone1999 1502 Example Q9 3-hydroxy-2-pentanone 1998 1500 Example Q101-phenyl-1-oxo-2-hydroxypropane 2000 1507 Example Q11 maleic anhydride(acid anhydride) 2000 1502 Example Q12 phthalic anhydride (acidanhydride) 2001 1503 Example Q13 fumaric anhydride (acid anhydride) 19991508 Example Q14 trimethylchlorosilane (silylating agent) 1999 1509Example Q15 tripentylchlorosilane (silylating agent) 2002 1500Comparative none 2001  799 Example Q1

EXAMPLE 18

Batteries R1 to R15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that dimethyldichlorosilane wasused as a coupling agent instead of 3-mercaptopropyltrimethoxysilane.The results are shown in Table 18.

TABLE 18 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example R1 dimethyldichloro- LiOHaqueous solution 2001 1500 Example R2 silane NaOH aqueous solution 20001504 Example R3 KOH aqueous solution 2001 1507 Example R4 ethylacetoacetate (β-diketone) 2000 1510 Example R5 2,4-pentadion(β-diketone) 2000 1500 Example R6 triethanol amine 2001 1509 Example R72-amino-2-methyl-1-propanol 1998 1508 Example R8 4-hydroxy-2-butanone1997 1500 Example R9 3-hydroxy-2-pentanone 1999 1503 Example R101-phenyl-1-oxo-2-hydroxypropane 1999 1507 Example R11 maleic anhydride(acid anhydride) 2001 1497 Example R12 phthalic anhydride (acidanhydride) 2002 1507 Example R13 fumaric anhydride (acid anhydride) 20011503 Example R14 trimethylchlorosilane (silylating agent) 1999 1502Example R15 tripentylchlorosilane (silylating agent) 2001 1509Comparative none 1998  797 Example R1

EXAMPLE 19

Batteries S1 to S15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that dimethyldimethoxysilane wasused as a coupling agent instead of 3-mercaptopropyltrimethoxysilane.The results are shown in Table 19.

TABLE 19 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example S1 dimethyldimethoxysilane LiOHaqueous solution 2002 1505 Example S2 NaOH aqueous solution 2000 1510Example S3 KOH aqueous solution 1999 1503 Example S4 ethyl acetoacetate(β-diketone) 2001 1500 Example S5 2,4-pentadion (β-diketone) 2003 1501Example S6 triethanol amine 2001 1505 Example S72-amino-2-methyl-1-propanol 1999 1508 Example S8 4-hydroxy-2-butanone1997 1507 Example S9 3-hydroxy-2-pentanone 2001 1498 Example S101-phenyl-1-oxo-2-hydroxypropane 2003 1508 Example S11 maleic anhydride(acid anhydride) 2000 1499 Example S12 phthalic anhydride (acidanhydride) 2001 1502 Example S13 fumaric anhydride (acid anhydride) 19981501 Example S14 trimethylchlorosilane (silylating agent) 2002 1500Example S15 tripentylchlorosilane (silylating agent) 1999 1502Comparative none 2000  795 Example S1

EXAMPLE 20

Batteries T1 to T15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that methyltrimethoxysilane wasused as a coupling agent instead of 3-mercaptopropyltrimethoxysilane.The results are shown in Table 20.

TABLE 20 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example T1 methyltrimethoxysilane LiOHaqueous solution 2002 1500 Example T2 NaOH aqueous solution 1999 1502Example T3 KOH aqueous solution 1998 1501 Example T4 ethyl acetoacetate(β-diketone) 2001 1503 Example T5 2,4-pentadion (β-diketone) 2001 1503Example T6 triethanol amine 1997 1500 Example T72-amino-2-methyl-1-propanol 2000 1500 Example T8 4-hydroxy-2-butanone1999 1508 Example T9 3-hydroxy-2-pentanone 2001 1497 Example T101-phenyl-1-oxo-2-hydroxypropane 1998 1500 Example T11 maleic anhydride(acid anhydride) 2001 1505 Example T12 phthalic anhydride (acidanhydride) 2002 1500 Example T13 fumaric anhydride (acid anhydride) 19991508 Example T14 trimethylchlorosilane (silylating agent) 2001 1498Example T15 tripentylchlorosilane (silylating agent) 2001 1509Comparative none 2002  800 Example T1

EXAMPLE 21

Batteries U1 to U15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except thatdiethoxymethyloctadecylsilane was used as a coupling agent instead of3-mercaptopropyltrimethoxysilane. The results are shown in Table 21.

TABLE 21 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example U1 diethoxymethyl- LiOH aqueoussolution 1998 1502 Example U2 octadecylsilane NaOH aqueous solution 20001507 Example U3 KOH aqueous solution 2000 1499 Example U4 ethylacetoacetate (β-diketone) 2000 1509 Example U5 2,4-pentadion(β-diketone) 1999 1502 Example U6 triethanol amine 2002 1505 Example U72-amino-2-methyl-1-propanol 2000 1510 Example U8 4-hydroxy-2-butanone2001 1500 Example U9 3-hydroxy-2-pentanone 2000 1510 Example U101-phenyl-1-oxo-2-hydroxypropane 1999 1507 Example U11 maleic anhydride(acid anhydride) 2001 1502 Example U12 phthalic anhydride (acidanhydride) 1999 1503 Example U13 fumaric anhydride (acid anhydride) 20001504 Example U14 trimethylchlorosilane (silylating agent) 2000 1502Example U15 tripentylchlorosilane (silylating agent) 2001 1509Comparative none 2001  799 Example U1

EXAMPLE 22

Batteries V1 to V15 were produced and evaluated in the same manner as inBatteries A1 to A15 of Example 1 except that diethoxydodecylmethylsilanewas used as a coupling agent instead of3-mercaptopropyltrimethoxysilane. The results are shown in Table 22.

TABLE 22 Intermittent cycle characteristic Charge/ Charge/ Dischargerest Discharge rest 30 min. 720 min. Discharge rate 1 CmA at 45° C.Coupling agent Stabilizer (mAh) Example V1 diethoxydodecyl- LiOH aqueoussolution 1999 1502 Example V2 methylsilane NaOH aqueous solution 20001500 Example V3 KOH aqueous solution 2000 1509 Example V4 ethylacetoacetate (β-diketone) 2000 1510 Example V5 2,4-pentadion(β-diketone) 1998 1502 Example V6 triethanol amine 2003 1501 Example V72-amino-2-methyl-1-propanol 2002 1500 Example V8 4-hydroxy-2-butanone2001 1509 Example V9 3-hydroxy-2-pentanone 1999 1507 Example V101-phenyl-1-oxo-2-hydroxypropane 2000 1503 Example V11 maleic anhydride(acid anhydride) 2000 1503 Example V12 phthalic anhydride (acidanhydride) 1998 1501 Example V13 fumaric anhydride (acid anhydride) 20021505 Example V14 trimethylchlorosilane (silylating agent) 2001 1500Example V15 tripentylchlorosilane (silylating agent) 2000 1499Comparative none 1998  800 Example V1

COMPARATIVE EXAMPLE

Comparative Example Batteries A1, B1, C1, D1, E1, F1, G1, H1, I1, J1,K1, L1, M1, N1, O1, P1, Q1, R1, S1, T1, U1, and V1 were prepared andevaluated in the same manners as in Batteries A1, B1, C1, D1, E1, F1,G1, H1, I1, J1, K1, L1, M1, N1, O1, P1, Q1, R1, S1, T1, U1, and V1,respectively, except that a stabilizer was not used. The results areshown in Tables 1 to 22.

In the above Examples, described are cases in whichnickel-cobalt-aluminum composite oxide was used as a lithium compositeoxide. However, lithium composite oxides having the general formula (1)have the similar crystal structure as LiCoO₂ or LiNiO₂ and have thesimilar properties, and thus the same effects are considered to beobtained from them. In addition, in cases wherein lithium compositeoxides contain Mn, Ti, Mg, Zr, Nb, Mo, W or Y instead of aluminum, ithas been confirmed that the similar results are obtained.

The present invention is useful in lithium ion secondary batteries thatcontain as active materials for positive electrode lithium compositeoxides having a main component of nickel or cobalt to further enhancecycle characteristic more than conventional one in a condition (e.g.intermittent cycle) closer to a practical use condition.

The shape of lithium ion secondary battery of the present invention isnot particularly limited, and may be formed in any shape, for example, acoin shape, button shape, sheet shape, cylindrical shape, flat shape,and square shape. Further, either of a winding type or stacking type maybe used as a configuration of electrode plate group comprising positiveand negative electrodes and a separator. Furthermore, the size of thebattery may be small for use in small portable devices or large for usein electric vehicles. Thus, the lithium ion secondary battery of thepresent invention can be used as power sources of, for example, personaldigital assistants, portable electronic devices, small power storagefacilities for household use, two-wheeled motor vehicles, electricvehicles, and hybrid electric vehicles. However, the use application isnot particularly limited.

Although the present invention has been described in terms of thepresently preferred embodiments, it is to be understood that suchdisclosure is not to be interpreted as limiting. Various alterations andmodifications will no doubt become apparent to those skilled in the artto which the present invention pertains, after having read the abovedisclosure. Accordingly, it is intended that the appended claims beinterpreted as covering all alterations and modifications as fall withinthe true spirit and scope of the invention.

1. A lithium ion secondary battery comprising a chargeable anddischargeable positive electrode, a chargeable and dischargeablenegative electrode, and a non-aqueous electrolyte, the positiveelectrode including an active material particle, the active materialparticle including a reaction product of a lithium composite oxide, thelithium composite oxide being represented by the general formula (1):Li_(x)M_(1-y)L_(y)O₂, where M is at least one selected from the groupconsisting of Ni and Co, and L is at least one selected from the groupof alkaline earth elements, transition elements other than Ni and Co,rare earth elements, and elements of Group IIIb and Group IVb, and where0.85≦x≦1.25 and 0≦y≦0.50; and a coupling agent having a plurality ofhydrolyzable groups and at least one functional group mercapto group,alkyl group, and fluorine atom, wherein the hydrolyzable group notforming a bond with the lithium composite oxide is reacted with aligating compound having two or more reactive groups and each of saidtwo or more reactive groups is hydroxyl group, carbonyl group, carboxylgroup, or alkoxy group.
 2. The lithium ion secondary battery accordingto claim 1, wherein 0<y, and L includes at least one selected from thegroup consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y.
 3. The lithiumion secondary battery according to claim 1, wherein the coupling agentis a silane coupling agent.
 4. The lithium ion secondary batteryaccording to claim 3, wherein at least one of the plurality of thehydrolyzable groups is at least one selected from the group consistingof alkoxy group and chlorine atom.
 5. The lithium ion secondary batteryaccording to claim 3, wherein the silane coupling agent binds to thelithium composite oxide via Si—O bond and forms a silicide compound onthe surface of the active material particle.
 6. The lithium ionsecondary battery according to claim 1, wherein the amount of thecoupling agent is 2% by weight or less with respect to the lithiumcomposite oxide.